Preheat oven to 350°F. Spray 3 quart baking dish with cooking spray and set aside.
In a large skillet over medium heat melt the butter. Once melted add the red onion, and bell peppers. Allow to cook for several minutes, stirring occasionally, until tender and browned.
Add in the garlic, cumin, chili powder, salt, and black pepper. Stir to coat the veggies in the seasonings.
Sprinkle the flour into the skillet. Stir to coat the veggies in the flour; you will end up with a thick paste.
Pour in the beef broth and stir. Bring mixture to a boil while stirring and let simmer while stirring for about 2-3 minutes until thick. Remove from heat, allow to cool for about 2 minutes and stir in the diced tomatoes with green chiles and the sour cream. Stir to combine. Add the shredded pork and stir until mixed. Set aside.
Heat a large griddle or skillet over medium heat. Brush the tortillas with the canola oil on both side and heat on the griddle until crisp and browned on each side.
Once all tortillas are browned, layer 6 tortillas on the bottom of the baking dish. Layer the tortillas to cover as much of the dish as possible. Top with half of the pork mixture then one third of the cheese. Repeat by layering 6 more tortillas, the remaining half of the pork mixture, and .one third of the cheese. Top with the remaining tortillas and the rest of the cheese.
Cover the baking dish with foil and bake for 15 minutes. Remove the foil and continue baking for an additional 10 minutes.
Remove from the oven allow to cool for several minutes then serve warm. Can serve with additional sour cream and fresh cilantro.